CONTRIBUTIONS FROM THE WISLEY LABORATORY. 121 



usually recurs in the following year. There seems little doubt that the 

 spores are able to outlive the winter, and it is therefore very desirable 

 that all such diseased refuse should be burned and not thrown upon 

 the rubbish heap. 



It must not, however, be overlooked that when the plants are 

 attacked the " seed " of the celery may be attacked too, just as in 

 most cases where the " seed " is in reality a fruit or a part of a fruit. 

 Figure 63 shows some " seeds " taken from a commercial seed sample 

 this season, having the fungus fruits upon them. It seems to be com- 

 paratively unusual to find them actually upon the fruit itself, though 

 this is not rare, but they are frequent upon the piece of stalk on which 

 the fruit grew, and which may or may not be still attached to the fruit. 

 Of thirty-three samples of celery seed examined in the Laboratory this 

 spring fourteen showed the perithecia of the fungus upon the seeds or 

 the pieces of stalk mixed with them, and microscopical examination 

 showed these perithecia in the majority of cases to contain spores still. 



Fig. 63. — Celery " seed," with the Fruit Bodies of the Fungus Septoria 



PETROSELINI VAR. APII SHOWING AS BLACK SPOTS UPON THEM. (MaG.) 



Some of these diseased seeds had been grown in England, others on the 

 Continent. 



At my request Mr. D. Finlayson, F.L.S., the well-known seed 

 expert of Wood Green, N., kindly washed several samples oi com- 

 mercial celery seed with distilled water, and microscopical examination 

 of the washings showed the spores of the fungus in 50 per cent, of them. 



Klebahn* has recently shown that washings from seeds saved from 

 diseased plants contain spores of the fungus, and by spraying healthy 

 plants with these washings he has infected them with the disease. 

 Indeed he believes the sowing of seeds containing the spores of the 

 fungus is the principal, if not the only, means of distributing the disease. 



In view of the fact that many samples of seed carry the spores of the 

 fungus, and that it has been shown that the spores obtained from the 

 seeds are infective, it would be well for growers to keep a keen watch 

 for the first sign of the disease in their plants, and to take prompt 

 measures to check the spread of the trouble as soon as it appears. 



* Klebahn, I.e. 



